Electric heating elements



Jan- 18, 1966 l.. D. DRUGMAND E'rAl. 3,230,492

ELECTRIC HEATING ELEMENTS Filed Dec. 5, 1962 Hq zo 50 Z ZZ /0 INVENTORS LESTER D. DRUGMAND m @y ALBEN (1.50665 United States `Patent O 3,230,492 ELECTRIC HEATING ELEMENTS Lester D. Drugmand and Alben C. Boggs, Pittsburgh,

Pa., assignors to Edwin L. Wiegand Company, Pittsburgh, Pa.

Filed Dec. 5, 1962, Ser. No. 242,420 Claims. (Cl. 338-274) The present invention relates to sheathed electric resistance heating elements and to methods of making the same, and the principal object of the invention is to provide new and improved methods and articles of the character described.

The manufacture of sheathed electric resistance heating elements, particularly for that class of elements employed as surface units in domestic ranges and the like, has long presented a problem in providing a low cost electrical connection to the element which will withstand the relatively severe service to which it will be exposed.

Heretofore, satisfactory electrical connections to elements of this type have only been made at relatively high manufacturing costs which must, of course, be passed on to the consumer. With the present invention, however, a very satisfactory connection, superior to many of those heretofore considered satisfactory, is provided at a cost far less than ever before. Other advantages will become apparent from a study of the following description and from the drawing appended hereto.

In the drawing accompanying this specification and forming a part of this application there is shown, for purpose of illustration, an embodiment which the invention may assume, and in this drawing:

FIGURE 1 -is a perspective View of `an electric resistance heating element of the surface, or range-top type,

FIGURE 2 is an enlarged, fragmentary view generally corresponding to the line 2 2 of FIGURE 1,

FIGURES 3 :and 4 are views similar lt-o FIGURE 2 but illustrating intermediate assembly stages, and

FIGURE S is a view similar to FIGURE 2 but showy ing a slightly modiiied construction.

With reference to FIGURE 1, the embodiment chosen to illustrate the present invention comprises an elongated metal sheathed heating element having its end portions `disposed in side-by-side relation and its intermediate portion 11 convoluted to provide a flat heating surface on which may be disposed a Vessel to be heated. As will later be pointed out with greater particularity, a flexible, insulated lead wire 12 is electrically connected t-o each of the element terminal ends 10 for connecting the element into a suitable electrical power circuit.

Turning now to FIGURE 2 wherein one of the element terminal ends is shown, it s to be understood that the heating element may be of the conventional type wherein a tubular metal sheath 13 is filledv with compacted, heat-resistant, electric-insulating material 14 in which is embedded a coiled resistor conductor 15 terminating short of respective sheath ends. At each sheathed end, a terminal conductor pin 16 is electrically and mechanically connected to the resistor 15 within the sheath and projects axially outwardly of the latter.

Still referring to FIGURE 2, lead wire 12 has an insulating covering 17 from which projects a bare wire portion 18. Wire portion 18 is 4disposed within one end of a tubular -connector 19 of metal or the like, the latter being crimped at 20 or otherwise mechanically and electrically secured to the lead wire portion 18. The other end of connector 19 is positioned over the projecting terminal pin 16 and is crimped at 21 or otherwise mechanically and electrically secured to the terminal pin. A dielectric plug 22 of resilient material, such as rubber or neoprene is tightly held within the sheath end ice portion preferably by inward deformation of this portion, such as during a normal operation wherein the sheath is passed between rolling dies to change its exterior from round to hexagonal. An end portion of the plug 22 preferably extends outward of the sheath, as shown.

Positioned over the connector 19 and extending between the end of tubular sheath 13 and the adjoining end of the wire covering 17, is a flexible, dielectric boot 23 of rubber or the like. For a purpose to appear, the boot 23 has close frictional engagement with the wire covering 17, the connector 19 and the element sheath 13. Boot 23 is moreover, cemented to the sheath, as by suitable cement 24, to insure against the entrance of deleterious substances such as grease, liquids or the like. It is to be understood, however, that the boot 23 may be vulcanized, clamped, or otherwise secured to the sheath 13 to insure a suitably sealed juncture therebetween.

It is an important feature of the invention that while the boot 23 is sealed to the element sheath 13, it has but close engagement with the connector 19 and the lead wire covering 17 as above described. This facilitates assembly as will appear and also provides for equalization of pressure between the interior of the element and the atmosphere since the interior of the element may breathe along the uncernented, frictionally fitting adjoining surfaces between the interior of the boot and exterior of the connector 19 and the lead wire 12. Notwithstanding the equalization aforesaid, the close iit of the boot over the wire covering and the connector, and the considerable length of close interengagement therebetween, effectively excludes deleterious substances from entering the element sheath.

Turning now to the method of assembling the element hereinabove described and with reference to FIGURE 3, the connector 19 and the boot 23 will -be assembled with the lead wire 12 as shown, the boot being spaced from the end of the lead wire so as not to interfere with assembling the connector to the wire by the previously mentioned crimping 20. The connector 19, and attached wire 12, are shifted in the direction of the arrow over the terminal pin 16 to the position seen in FIGURE 4. Connector 19 may now be crimped to the terminal pin as indicated at 21.

With the parts positioned as seen in FIGURE 4, a suitable cement 24 may be deposited on the sheath 13 as shown, it being understood, however, that such cement may also be deposited on the sheath at an earlier stage of assembly. Boot 23 will next be shifted in the direction of the arrow from the position seen in FIGURE 4, over the connector 19 .and over the end of the sheath to the position seen in FIGURE 2. Boot 23 will next preferably be rotated 360 about its axis and relative to the element shea-th 13, the pin 16 and the lead wire 12 to insure even distribution of the cement 24 about the sheath periphery. Following hardening of the cement 24, the heating element assembly may be placed in service. The cement is preferably of the type which vulcanizes at room temperature. A cement of this type is commercially available and is designated Dow RTV #731.

While only one element end 10 has been described in detail, it will be understood that both ends are preferably identical.

Use of the modification shown in FIGURE 5 is contemplated in applications involving low operating ternperatures and humid environments where a `sealed type terminal would be desirable. As seen in FIGURE 5, the bore through the connector 19 is interrupted to provide an internal barrier 30. This barrier will positively prevent passage of moisture along the stranding of the wire 13 to the terminal pin 16 and therefrom to the interior of the heating element.

In the modication of FIGURE 5, the boot 23 is also ysealed to the lead wire 12 and preferably is cemented to insulating covering 17, connector 19 and plug 22. One way of easily effecting such sealing action is to hold upright the assembly shown in FIGURE 4 with the opening into the boot 23 uppermost. Suitable pourable cement, such as Dow RTV #731, may be poured into the boot opening to substantially iill the same. The boot 23 may then be elevated to the final assembly shovm in FIGURE 2, relative rotation of Ithe boot and sheath insuring distribution of the cement. The cement may be air cured and the heating element then stored or put into use. In this embodiment, the interior surface of the boot is cemented to the exterior surfaces of the insulation 17, connector 19, plug 22 (see cement deposit 31 iilling space between plug and boot) and sheath 13, and moisture is effectively prevented from entering the heating element.

In view of the foregoing, it will be apparent to those skilled in the art that we have accomplished at least the principal object of our invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and moditied, Without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that our invention is not limited thereto.

We claim:

1. In an electrical heater of the tubular type having a tubular sheath provided with an open e-nd, a resistance conductor within said sheath, a terminal pin electrically connected to said conductor and extending through and beyond said open end, electrically-insulating heat-conducting material Within said sheath for insulating said conductor and said terminal pin from said sheath, an insulated lead wire having a bared end electrically connected to the outwardly projecting portion of said terminal pin .and mechanically connecting said sheath and said lead Wire generally in coaxial relation, and a dielectric body of a length to extend from an end portion of said sheath to an end portion of the insulation of said lead wire and surrounding said sheath and insulation end portions and the electrical connection between said terminal pin and the bared end of said lead wire, said body being sealed to said sheath end portion to prevent entrance of deleterious substances at this place, and said body having an unsealed close lit with said insulation end portion to restrict passage of deleterious substances along the insulation and to the interior ot said sheath and yet permitting ow of gas to and from the sheath interior along the insulation.

2. The construction according to claim 1, wherein said dielectric body is preformed of a rubber-like material, its inherent resiliency causing it to lit snugly around said insulation end portion.

3. In an electrical heater of the tubular type having a tubular sheath provided with an open end, a resistance conductor within said sheath, a terminal pin electrically connected to said conductor and ex-tending through and beyond said open end, electrically-insulating heat-oonducting material within lsaid sheath for insulating said conductor and said terminal pin from said sheath, an insulated lead wire having a bared end, a metallic connector having one end portion generally of the same transverse size as the insulation of said lead wire and having an opening entering this end for closely receiving said bared Wire end, said connector having an opposite end portion generally of the same transverse size as the internal size of said sheath open end and having an opening entering said oppo-site end portion to closely receive said terminal pin, said latter opening being coaxial with the first named connector opening whereby said sheath and said lead wire are mechanically connected in end-toend relation, and a tubular body of preformed rubberlike material of a length to extend from an end portion of said sheath to an end portion of the insulation at said bared end and surrounding said sheath and insulation end portions and said connector, the smallest opening in said body being of a size to resiliently but slidably t on the lead wire insulation so that said body may be slid to a position to be away from said bared end of said lead wire so that electrical connections between said connector end portions and respective bared end and terminal pin may be made, whereupon said body may be slid along said lead Wire insulation to position closely enclosing said sheath and lead wire end portions and the connector intermediate the same.

4. The construction of claim 3 wherein said rubberlike body has an end opening receiving said sheath end portion, the latter having a sealed connection with the surface defining said end opening.

5. The construction of claim 4 wherein a sealed connection is provided between the body surface defining said smallest opening and the insulation of said lead wire after said body has been slid along said lead wire to position closely enclosing said sheath and lead wire end portions and the connector intermediate the same.

References Cited by the Examiner UNITED STATES PATENTS 1,669,385 5/1928 Wiegand et al. 29-155.64 2,009,980 7/ 1935 Abbott 338-241 2,043,195 6/ 1936 Finlayson 29-155.69 2,046,102 6/ 1936 Abbott 338-241 X 2,352,159 6/1944 Brodie l7477 2,659,795 11/1953 Boggs 338-238 X 2,807,696 9/1957 Boggs et al. 338-238 X 2,824,199 9/1958 Browne 338-241 2,876,322 3/1959 Boggs 338-274 X 2,944,325 7/ 1960 Clark 29-155.55 3,010,184 11/1961 Fourney 29-155.55 3,036,368 5/1962 Felts 29-l55.69 3,113,284 12/ 1963 Van Inthoudt 338-274 RICHARD M. WOOD, Primary Examiner. 

1. IN AN ELECTRICAL HEATER FOR THE TUBULAR TYPE HAVING A TUBULAR SHEATH PROVIDED WITH AN OPEN END, A RESISTANCE CONDUCTOR WITHIN SAID SHEATH, A TERMINAL PIN ELECTRICALLY CONNECTED TO SAID CONDUCTOR AND EXTENDING THROUGH AND BEYOND SAID OPEN END, ELECTRICALLY-INSULATING HEAT-CONDUCTING MATERIAL WITHIN SAID SHEATH FOR INSULATING SAID CONDUCTOR AND SAID TERMINAL PIN FROM SAID SHEATH, AN INSULATED LEAD WIRE HAVING A BARED END ELECTRICALLY CONNECTED TO THE OUTWARDLY PROJECTING PORTION OF SAID TERMINAL PIN AND MECHANICALLY CONNECTING SAID SHEATH AND SAID LEAD WIRE GENERALLY IN COAXIAL RELATION, AND A DIELECTRIC BODY OF AN LENGTH TO EXTEND FROM AN END PORTION OF SAID SHEATH TO AN END PORTION OF THE INSULATION OF SAID LEAD WIRE AND SURROUNDING SAID SHEATH AND INSULATING END PORTIONS AND THE ELECTRICAL CONNECTION BETWEEN SAID TERMINAL PIN AND THE BARED END OF SAID LEAD WIRE, SAID BODY BEING SEALED TO SAID SHEATH END PORTION TO PREVENT ENTRANCE OF DELETERIOUS SUBSTANCES AT THIS PLACE, AND SAID BODY HAVING AN UNSEALED CLOSE FIT WITH INSULATION END PORTION TO RESTRICT PASSAGE OF DELETERIOUS SUBSTANCES ALONG THE INSULATING AND TO THE INTERIOR OF SAID SHEATH AND YET PERMITTING FLOW OF GAS TO AND FROM THE SHEATH INTERIOR ALONG THE INSULATION. 